The proposed project will study the relationship between protein deficiency and reproduction. The effect of a low protein diet (LPD), consisting of 8% protein, will be examined in male and female Sprague-Dawley rats from birth through adulthood. Serum and pituitary luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin (PRL) will be quantitated by radioimmunoassay and a morphological analysis will be conducted on the pituitary gland, the gonads and the accessory sex organs. The influence of protein deficiency on fertility will be studied in male and female rats maintained on the LPD from birth through sexual maturity. The aforementioned gonadotrophic hormones will also be measured at selected time intervals in rats given the LPD throughout pregnancy and lactation. Lastly, the influence of protein deficiency on the suckling-induced release of PRL will be studied at time periods during which the pups are actively suckling and at intervals following the removal of the pups.